screen-share: get previous_damage from data argument instead of weston_output

Instead of getting previous_damage from the weston_output struct, get it from
the frame_signal data argument. This will make possible to remove
previous_damage from weston_output after we decide what to do with
output->previous_damage usage in DRM backend.

Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>

compositor/screen-share.c

@@ -847,8 +847,7 @@ shared_output_repainted(struct wl_listener *listener, void *data)
 	} else {
 		/* Damage in output coordinates */
 		pixman_region32_init(&damage);
-		pixman_region32_intersect(&damage, &so->output->region,
-					  &so->output->previous_damage);
+		pixman_region32_intersect(&damage, &so->output->region, data);
 		pixman_region32_translate(&damage, -so->output->x, -so->output->y);
 	}